Which of the Following Is NOT a Reason Why the Data

Which of the following is NOT a reason why the data probably undercount the number of cohabiting couples?

A) Researchers have not been interested in cohabitation and so have not asked couples about their living status.
B) The Census Bureau does not tabulate all unmarried couples in a home but only the person who rent or owns the residence and her or his unmarried partner.
C) Unmarried couples may be reluctant to disclose that they are living together.
D) Couples that feel they are in a common-law marriage may not describe themselves as "unmarried partners."